OBJECTIVE - is a frequently amplified and overexpressed gene that promotes several oncogenic functions in gastric cancer. Herein, we investigated the relationship between infection, proinflammatory NF-κB activation and regulation of DARPP-32.
DESIGN - The study used and experiments. Luciferase reporter, quantitative real-time PCR, immunoblot, chromatin immunoprecipitation (ChIP), cell viability, infection, tissue microarrays and immunohistochemical assays were used.
RESULTS - Our results indicated that infection increased the DARPP-32 mRNA and protein levels in gastric cancer cell lines and gastric mucosa of mice. infection increased the activity of NF-κB reporter and p-NF-κB (S536) protein level and . To investigate the transcriptional regulation of DARPP-32, we cloned a 3019 bp of the promoter into the luciferase reporter (pGL3-Luc). Both infection and tumour necrosis factor-α treatment induced DARPP-32 reporter activity (p<0.01). Using deletion constructs of promoter and ChIP assay, we demonstrated that the sequence -996 to -1008 bp containing putative NF-κB-binding sites is the most active region. The induction of DARPP-32 expression by infection counteracted -induced cell death through activation of serine/threonine-specific protein kinase (AKT), as determined by ATP-Glo and clonogenic survival assays. Immunohistochemistry analysis demonstrated a significant positive correlation between NF-κB and DARPP-32 expression levels in gastric cancer tissues (r=0.43, p<0.01).
CONCLUSIONS - Given the high frequency of DARPP-32 overexpression and its prosurvival oncogenic functions, the induction of DARPP-32 expression following infection and activation of NF-κB provides a link between infection, inflammation and gastric tumourigenesis.
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